多孔介质中天然气水合物二维开采实验模拟研究
文献类型：学位论文
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| 作者 | 杜燕 |
| 学位类别 | 博士 |
| 答辩日期 | 2008-06-02 |
| 授予单位 | 中国科学院广州能源研究所 |
| 授予地点 | 广州能源研究所 |
| 导师 | 冯自平 |
| 关键词 | 天然气水合物 电容 降压 注化学剂 二维 数值模拟 |
| 其他题名 | Experimental Study of Production of Natural Gas Hydrate in Porous Media with the 2D Experimental System |
| 中文摘要 | As a greatly potential alternative energy resource, natural gas hydrates (NGH) is of high quality and burns clean. The production technologies of NGH have the great significance in view of theory and practice. Through mechanisms analysis, experiments and numerical simulation technology studied systematically, the law of formation and decomposition of NGH in porous medium and two production methods of depressurization and chemical inhibitor stimulation were discussed in this paper. By the analysis of variation of parameters, including temperature, pressure and gas production rate, a comprehensive understanding about production mechanism, dynamic characteristics and influencing factors was achieved, and furthermore, the all-round evaluation about these methods were developed. A set of Two-dimensional experimental system for the production of NGH in porous media was designed. The system consists of seven modules, which are water supplying, gas supplying, formation and decomposition simulating, environment simulating, backpressure regulating, pressure、temperature and flow flux metering, data acquiring. Capacity technology was also used to measure the phase development in the process of NGH formation and dissociation. The system can be used in NGH formation experiment in porous media and in diverse decomposition experiments as well, such as depressurization, thermal stimulation and chemicals injection. The changing tendency of temperature and pressure in the NGH formation and dissociation prove the experimental apparatus and method are reliable. The formation rates of NGH are much higher than those reported by other researchers and induction time decreased to five minutes at most. Annealing process would lengthen the formation and the first experiment is always the most timesaving, which suggests that memory effects does not exist widely. Special development curves of pressure show that nucleation is not always essential for the complete growth of hydrate crystals. Experiments displayed similar reproducibility and development law in the vessel with the larger volume or larger surface area. Water content is the most important influential factor in the capacity measurement. In the formation experiment, capacity becomes lower as water volume decreased because of formation of NGH. The validity of the capacity technology used in NGH is proved, especially its significance in investigating the flowing characteristics of the gas and water in formation and dissociation in porous media. In the condition of this experiment, depressurization is an effective method of NGH production, because of its high gas production rate that is mainly controlled by depressurizing rate and steady low water production rate. Moreover, it costs less unnecessary to stimulate continuously. Flow and dissociation mechanism are the most important controlling factors in depressurization. The conclusion can be made that hydrate dissociation process is kinetic-controlled for the first kind of 2D simulators with low NGH saturation and high permeability and flow-controlled for the second kind simulator with high NGH saturation and lower permeability. Great temperature decrease can be gained by minimum pressure drop which most be likely to induce the reformation of NGH in the sediment at the well bottom. As a result, gas flux towards the well decrease, which consequently reduce the exploitation quantity. Consideration of the heat transfer characteristics of natural NGH reservoir, it is important to control the depressurize rate for the exploitation of NGH successfully. In addition, it is considered to heat injection or inhibitor injection as auxiliary strengthening measures. Decomposition rate constant and permeability are two most important factors that influence the gas production performance in simulation. For the laboratory-scale reservoir, the peak value of gas production rate increases and the decomposition time shortens with the increase of decomposition rate constant. The variation of absolute permeability almost has no effects on the production behavior. Under the condition of this experiment, the production efficiency by chemicals injection (the volume of the output gas under the standard condition in a time unit when a mass unit of chemical inhibitor is injected) is increasing with the solution concentration and the injection rate. Multi-well production has higher efficiency than that of single-well production with the identical concentration and injection rate. Compared with the well-layout of NGH production, solution concentration and injection rate have the greater impacts on the production efficiency. But truthfully, it is not the case for the naturally occurring hydrate reservoirs. The variations of temperature field with the time elapsing reflect directly the advancement of hydrate dissociation front. The fact that limited sweep region of chemical inhibitor cause a large quantity of NGH production failed, which indicates that chemical inhibitor method used alone for NGH production is unfeasible. In the real exploitation of natural NGH reservoir, the method of “chemical inhibitor solution slug and ambient temperature water displacement” can be applied, or with depressurization method combined. This model should be proposed for NGH production that to combine depressurization with inhibitor injection simulation, considering the latter as the strengthening measure of the former. |
| 语种 | 中文 |
| 公开日期 | 2011-07-10 ; 2011-07-15 |
| 页码 | 127 |
| 源URL | [http://ir.giec.ac.cn/handle/344007/4061]  |
| 专题 | 中国科学院广州能源研究所 |
| 推荐引用方式 GB/T 7714 | 杜燕. 多孔介质中天然气水合物二维开采实验模拟研究, Experimental Study of Production of Natural Gas Hydrate in Porous Media with the 2D Experimental System[D]. 广州能源研究所. 中国科学院广州能源研究所. 2008. |
入库方式： OAI收割
来源：广州能源研究所
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